1. Field of the Invention
The present invention relates to an instrument for determining an appropriate dose of a liquid chemical sterilant to be injected into a testis of an animal having scrotal testes and to a method for determining the dose with the instrument.
2. Brief Description of the Prior Art
Various chemical agents have been injected into the testes for the purpose of interfering with the production of sperm in the seminiferous tubules. Many effective chemicals have been found too harsh to be used practically. An effective and biologically acceptable chemical sterilant was described in U.S. Pat. Nos. 4,937,234 and 5,070,080 to Fahim. In the '080 patent, the chemical sterilant was injected into the midline at the side or bottom of each testis. Depending upon the dose administered, spermatogenesis in the seminiferous tubules was completely stopped. It was later found that if the injection is given into the dorsal cranial portion of the testis, lesser amounts of chemical sterilant is needed to effect complete sterilization.
The effective dose depends on the concentration of the active ingredients in the aqueous solution and the size of the testis. Injecting too large a volume may rupture the testis and too large a dose may be harmful to the animal. Testis size, however, does not correlate with body weight so that the dose cannot be determined by weighing the animal. For example, dogs of different breeds having the same weight may have different sized testes. Even dogs of the same breed and having the same weight may have different sized testes. It also occurs that the testes of the same dog may be different in size. Hence the size of the testis of each animal must be measured to determine the dose to be injected to effect sterilization.